Epidemiologic and mechanical studies suggest that cyclic loading is an important etiologic risk factor in the development of degnerative disc disease. Posture, spinal stiffness, asymmetric spinal loading and abdominal tone appear to influence the effects of vibration. By analysis of a general practice population and questionnaire survey, we will define the role of cyclic loading in the broader perspective of low back pain (LBP). Sub-groups with and without back pain, with and without significant vibrational loadings will be identified. These sub-groups will then be investigated by questionnaire, and by standardized physical examination for spine stiffness, posture, straight leg raising, and neurologic abnormality, using biomechanical test methods including Moire fringe topography. Psychologic factors will be evaluated by computerized modified Minnesota Multiphasic Personality Index (MMPI), pain drawings and tolerance tests. Objective radiographic analysis will correlate LBP with postural, congenital, disc space height, and facet characteristics. The load deflection and impedance characteristics will be measured. By case studies, the environmental vibrational stresses, lifting requirements, and asymmetric loading configurations imposed on the spine will be analyzed. (Safety standards will be recommended for vibrational stresses.)